1. Field of the Invention
The present invention relates to tunable laser systems, and more particularly to relatively high energy tunable systems with narrow line widths.
2. Description of Related Art
Tunable laser systems with relatively high output energies and narrow line widths have a number of scientific and engineering applications. Most such systems are implemented using dye lasers which are based on gain media dyes, each of which are tunable over a range of 15-100 nanometers. These systems are desirable because of the narrow line widths and relatively high energy that is achievable. However, dye laser systems are cumbersome for applications requiring a wide tunable range, because the dye gain medium must be changed as the output is tuned beyond the 15 or 100 nanometer range of the particular dye being used.
Optical parametric oscillators and amplifiers provide another technique for providing a tunable system. OPOs are particularly interesting because of the wide range of tunability which can be achieved using the same. For instance, OPOs using .beta.-barium borate (BBO) as the optical gain material have achieved tunable ranges from less than 400 nanometers to over about 2500 nanometers. These systems are tunable by rotating the angle of the crystal relative to the optical path using servo techniques well known in the art.
Master oscillator/power oscillator designs based on injection seeding have been applied to BBO based OPO designs. However, the outputs of such systems have relatively broad band output pulses of greater than 1 cm.sup.-1, with energies of up to 50 mJ per pulse. However, no higher energy and narrower line width systems have been achieved. For instance, power oscillator OPO cavities injection seeded with narrow band laser sources, such as laser diodes or dye lasers, have been implemented. Resulting output of these systems is relatively high energy and narrow line. However, laser diode or dye laser type injection seeded OPOs have not been of any commercial value because of the severe limitations in tuning the diodes of .+-.5 nanometers, or of the dyes of .+-.50 nanometers. Dye based laser systems also lose the desired elegance of all solid state systems, since the liquid dyes themselves degrade and are consumable.
Prior art OPO systems, however, have been unable to achieve narrow line widths in combination with broad tunability and with sufficiently high power for commercial application. Thus, it is desirable to provide a broadly tunable system supplying laser light with relatively high energy and narrow line width outputs.